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Title: Laurel wilt: An unusual and destructive disease of American members of the Lauraceae

Author
item PLOETZ, R - University Of Florida
item SMITH, J - University Of Florida
item HUGHES, M - University Of Florida
item INCH, S - University Of Florida
item DREADEN, T - University Of Florida
item SPENCE, D - University Of Florida
item CARRILLO, D - University Of Florida
item DUNCAN, R - University Of Florida
item PENA, J - University Of Florida
item Kendra, Paul
item SANDARAN, S - University Of Florida
item EHSANI, R - University Of Florida
item HELD, B - University Of Florida
item BLANCHETTE, R - University Of Florida
item CAMPBELL, A - University Of Florida
item WHITE, T - University Of Florida

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/20/2012
Publication Date: 8/12/2012
Citation: Ploetz, R., Smith, J., Hughes, M., Inch, S., Dreaden, T., Spence, D., Carrillo, D., Duncan, R., Pena, J., Kendra, P.E., Sandaran, S., Ehsani, R., Held, B., Blanchette, R., Campbell, A., White, T. 2012. Laurel wilt: An unusual and destructive disease of American members of the Lauraceae. Meeting Abstract. Ambrosia Beetle/Fungal Symbiont Workshop.

Interpretive Summary: Laurel wilt kills American members of the Lauraceae plant family (Laurales, Magnoliid complex). These include significant components of Coastal Plain forest communities in the SE USA, most importantly redbay (Persea borbonia), as well as the commercial crop avocado (P. americana). Laurel wilt is caused by the ascomycete Raffaelea lauricola (Ophiostomatales), which has an Asian ambrosia beetle, Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), as a vector. In May 2002, X. glabratus was reported for the first time in the Western Hemisphere in Port Wentworth, GA. Laurel wilt is now widely spread in the SE USA due to its mobile insect vector, the movement of infested wood, and the presence of native and non-native plants that are susceptible to the disease and on which the vector reproduces. Diverse strategies have been examined for managing laurel wilt, including host resistance (avocado and redbay), the use of fungicides (avocado and redbay), and insecticides and repellents (avocado). To date, no highly efficacious and cost-effective measure has been identified. In the absence of such a measure cultural methods, in particular the prompt identification, removal and destruction of infected/infested trees (sanitation), will play significant roles in disease mitigation. Ongoing work investigates a remote sensing method to rapidly identify affected trees. In artificially inoculated avocado, plant size was positively correlated with disease severity. Since significant symptoms develop internally in the sapwood before external symptoms are evident, management of the disease with fungicides or other means will be difficult if measures are delayed until after external symptoms develop. Despite its rapid acropetal and basipetal movement in host xylem, R. lauricola is scarcely evident in affected plants. Microscopic localization of the fungus and its detection via DNA analyses is inconsistent, especially in avocado. Vascular function and hydraulic conductivity is dramatically reduced in affected avocado. The pathogen has been recovered from nine species of scolytines that have been recovered from laurel wilt-affected avocado, redbay and swampbay. Compared to X. glabratus, fewer propagules of R. lauricola have been detected in other beetle species (100s or 10s vs 1,000s). However, the rarity of X. glabratus in laurel wilt-affected avocado (no or very few individuals of this species are recovered from this host) and what appear to be sufficient levels of inoculum in several of the other species to cause disease raised the possibility that X. glabratus is not the only vector of this pathogen. Recently, this possibility was confirmed on avocado and redbay. Other means by which the pathogen could be transmitted include movement via root grafts (probable), pruning equipment (less likely), and avocado fruit, seed and scion material (doubtful).

Technical Abstract: Laurel wilt kills American members of the Lauraceae plant family (Laurales, Magnoliid complex). These include significant components of Coastal Plain forest communities in the SE USA, most importantly redbay (Persea borbonia), as well as the commercial crop avocado (P. americana). Laurel wilt is caused by the ascomycete Raffaelea lauricola (Ophiostomatales), which has an Asian ambrosia beetle, Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), as a vector. In May 2002, X. glabratus was reported for the first time in the Western Hemisphere in Port Wentworth, GA. Laurel wilt is now widely spread in the SE USA due to its mobile insect vector, the movement of infested wood, and the presence of native and non-native plants that are susceptible to the disease and on which the vector reproduces. Diverse strategies have been examined for managing laurel wilt, including host resistance (avocado and redbay), the use of fungicides (avocado and redbay), and insecticides and repellents (avocado). To date, no highly efficacious and cost-effective measure has been identified. In the absence of such a measure cultural methods, in particular the prompt identification, removal and destruction of infected/infested trees (sanitation), will play significant roles in disease mitigation. Ongoing work investigates a remote sensing method to rapidly identify affected trees. In artificially inoculated avocado, plant size was positively correlated with disease severity. Since significant symptoms develop internally in the sapwood before external symptoms are evident, management of the disease with fungicides or other means will be difficult if measures are delayed until after external symptoms develop. Despite its rapid acropetal and basipetal movement in host xylem, R. lauricola is scarcely evident in affected plants. Microscopic localization of the fungus and its detection via DNA analyses is inconsistent, especially in avocado. Vascular function and hydraulic conductivity is dramatically reduced in affected avocado. The pathogen has been recovered from nine species of scolytines that have been recovered from laurel wilt-affected avocado, redbay and swampbay. Compared to X. glabratus, fewer propagules of R. lauricola have been detected in other beetle species (100s or 10s vs 1,000s). However, the rarity of X. glabratus in laurel wilt-affected avocado (no or very few individuals of this species are recovered from this host) and what appear to be sufficient levels of inoculum in several of the other species to cause disease raised the possibility that X. glabratus is not the only vector of this pathogen. Recently, this possibility was confirmed on avocado and redbay. Other means by which the pathogen could be transmitted include movement via root grafts (probable), pruning equipment (less likely), and avocado fruit, seed and scion material (doubtful).